The view hierarchy will refresh when you interact with the app (since it's reasonable to expect that the app's state doesn't change unless the user interacts with it).

To get a fresh view hierarchy, you can either tap on the app: app.tap() and then print the debug description, or you could create a new instance of XCUIApplication and use that instead of the existing app property which has the cached view hierarchy. The new instance should show a fresh view hierarchy.